1. Field of the Invention
The present invention relates to a CMOS type image pick-up element that realizes the micro formation, the high function and the high sensitivity of a picked up image of a visible light.
2. Description of the Related Art
FIG. 4 is a diagram showing one example of a structure of the related-art CMOS type image sensor. The CMOS type image sensor is considered to be promising, like a CCD type image sensor, from the viewpoint that an integrated circuit similar to a one-chip camera can be realized by integrating a microlens for converging incident lights, a spectral filter, an optical element part provided with a photodiode for carrying out a photoelectric conversion and a signal storage, a signal scanning part for scanning stored signals, a gain control amplifier for amplifying the signal as an output and signal processing circuit parts such as a sample hold circuit for removing noise, an analog/digital converting circuit or the like. The related-art image sensors are disclosed in JP-A-2007-13089 and JP-A-1-102321.
However, the CMOS type image sensor has a problem that the scale of the circuit parts except the optical element part is enlarged, and includes problems in view of below-described points.
(1) Since a multi-layer wiring is introduced due to the high function of the peripheral circuit and the matching characteristics of a color filter process or a microlens process are not good, optical characteristics are inferior to those of the CCD image sensor.(2) When the scale of the peripheral circuits is enlarged, a cost is increased owing to the loss of the peripheral circuit that is inferior due to the defect of an image.(3) When a pixel is micronized, an optical path for guiding the incident light to the surface of a silicon substrate needs to be maintained to a size having a prescribed ratio to a wavelength so that an occupation rate of the photodiode is disadvantageously increased in the pixel to achieve a micro formation and a high function.